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Specifications
Specifications
Gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge
Length	71 ft 2 in (21.69 m) over the coupler pulling faces
Prime mover	EMD 16-645F3B
Engine type	V16 diesel
Alternator	main : AR11
Cylinders	16

Type and origin
Type and origin
Power type	Diesel-electric
Builder	Electro-Motive Diesel; General Motors Diesel; Clyde Engineering
Model	SD50
Build date	December 1980 – July 1987
Total produced	431

EMD SD50
EMD SD50
	An SD50 operated by Kansas City Southern Railway
Power type
Type and origin
Power type	Diesel-electric
Builder	Electro-Motive Diesel; General Motors Diesel; Clyde Engineering
Model	SD50
Build date	December 1980 – July 1987
Total produced	431
Gauge
Specifications
Gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge
Length	71 ft 2 in (21.69 m) over the coupler pulling faces
Prime mover	EMD 16-645F3B
Engine type	V16 diesel
Alternator	main : AR11
Cylinders	16
Power output
Performance figures
Power output	3,500 hp (2,610 kW) at 950 rpm; increased to 3,600 hp (2,685 kW) November 1984.
Operators
Career
Operators	See Original buyers
Disposition	Some in service, some retired, one preserved

The EMD SD50 is a 3,500-horsepower (2,610 kW) diesel-electric locomotive built by General Motors Electro-Motive Division. It was introduced in May 1981 as part of EMD's "50 Series"; production ceased in January 1986. The SD50 was a transitional model between EMD's Dash 2 series which was produced throughout the 1970s and the microprocessor-equipped SD60 and SD70 locomotives. A total of 431 were built.^[1]

History

The SD50 was produced in response to increasingly tough competition from GE Transportation, whose Dash 7 line was proving quite successful with railroads. While EMD's SD40-2 was a reliable and trusted product, GE's line included locomotives up to 3,600 hp (2,685 kW) with more modern technology, as well as very competitive finance and maintenance deals. EMD responded throughout the SD50 program by offering discounts on large orders.

The GM-EMD locomotives that immediately preceded the SD50, the 3,600 hp (2,685 kW) SD45 and SD45-2, used huge, 20-cylinder engines that consumed large amounts of fuel and suffered from reliability problems when first introduced. Demand for the 45 series dropped sharply after the 1970s fuel crisis. The SD50 used an updated version of the V16 645 from the SD40-2, uprated to 3,500 hp (2,600 kW) at 950 rpm from 3,000 hp (2,240 kW) at 900 rpm, and uprated again in November 1984 to 3,600 hp (2,685 kW). This proved to be a step too far; the 50 series models were plagued by engine and electrical system problems which harmed EMD's sales and reputation.

Compared with their predecessors, the SD50 had a longer frame and a substantially longer long hood. In addition, the resistors for the dynamic brake grid were moved from their location on previous models above the prime mover to a new, cooler location in front of the engine compartment air intakes, closer to the electrical switchgear. This increased their separation from other systems, simplifying maintenance for the prime mover and the electrical system.

One former SD50 engineer praised the locomotives' wheel-slip control system and dynamic braking power, stating "they were able to give more adhesion than a SD40-2".^[2]

Technical

The SD50 is powered by V16 16-645F3 series diesel engine driving either an EMD AR11A-D14 or an EMD AR16A-D18 traction alternator. The power generated by the traction alternator drove 6 EMD D87 traction motors rated at 1170 amps each.

The SD50 was available with multiple traction motor gearing ratios and wheel sizes, the most common of which was the 70:17 ratio with 40-inch (1,016 mm) wheels, which allowed for a top speed of 70 mph (110 km/h). Other gearing options for the SD50 with 40-inch (1,016 mm) wheels included 69:18 for 76 mph (122 km/h), 67:19 for 82 mph (132 km/h) and 66:20 for 88 mph (142 km/h). The SD50 was also available with 42-inch (1,067 mm) wheels.

The SD50 was also available with either HT-C trucks (identified with a hydraulic shock on the side of the middle axle of each truck) or the earlier Flexicoil trucks. Some investigators implicated the HT-C truck in derailments of Amtrak's SDP40Fs, so Conrail chose the Flexicoil C trucks for their SD40-2s and their first order of SD50s—the only customer to do so. The controversy surrounding the HT-C truck was eventually disproved, and Conrail chose HT-C trucks for their second order of SD50s and SD60s.

SD50S

The SD50S ("short frame") were prototype units built in December 1980. They were shorter than production locomotives by approximately 2 feet (0.61 m). There were six SD50Ss built, all of which were sold to the Norfolk & Western and eventually passed to Norfolk Southern. They were withdrawn in the early 2000s as non-standard. Two were rebuilt in 2008 as "SD40E" models by Norfolk Southern's Juniata Shops, along with several standard length SD50s.

The SD50S designation was also used for five locomotives built by EMD Australian licensee Clyde Engineering, Adelaide for Hamersley Iron.^[3] Shorter than production SD50s, they were equipped with a special double cab roof for insulation against the hot Australian desert sun in the Pilbara region. Withdrawn in November 1995, they were sold to National Railway Equipment Company and exported to the United States in February 1999 and used in national lease service.^[4] They were subsequently sold to the Utah Railway in June 2001.^[5]^[6] In June 2017, 6063 and 6064 were sold to the Chicago, Fort Wayne & Eastern Railroad, 6064 was relocated by Genesee & Wyoming to the Indiana & Ohio Railway and renumbered 5016 and 5017.^[7]

SD50F

The SD50F was a Canadian cowl unit version equipped with a "Draper taper" (inset section aft of cab for limited rear visibility). Sixty were built for the Canadian National Railway as road numbers 5400–5459. Early engine problems resulted in a temporary down-rating to 3,300 horsepower (2,500 kW). Eventually the units were re-rated to 3,500 horsepower (2,600 kW); however, like their U.S. cousins, they continued to suffer from relatively low reliability, frequently suffering engine, power assembly, and crankshaft failures.

Original owners

Railroad	Qty.	Road numbers	Notes	References
SD50
Baltimore & Ohio (Chessie System)	20	8576–8595
Chicago & North Western	35	7000–7034	7009 donated to the Illinois Railway Museum	^[2]
Chesapeake & Ohio (Chessie System)	43	8553–8575, 8624–8643
Conrail	135	6700–6834
Denver & Rio Grande Western	17	5501–5517
Kansas City Southern Railway	10	704–713
Missouri Pacific Railroad	60	5000–5059
Seaboard System Railroad	81	8500–8552, 8596–8623
Norfolk Southern	20	6506–6525
Hamersley Iron	5	6060–6064
SD50S
Norfolk & Western Railway	6	6500–6505	SD50S short frame
SD50F
Canadian National	60	5400–5459	Cowl units
Totals	431

Rebuilds

A number of SD50s have been rebuilt into the equivalent of SD40-2s. The Dash 2 features are already contained within the SD50. The units are derated from 3,500 hp (2,600 kW) at 950 rpm to 3,000 hp (2,200 kW) at 900 rpm. This is actually a quite simple change to the locomotive's Woodward PGE engine governor.

Preservation

• In late October 2022, the Illinois Railway Museum acquired former Chicago & North Western #7009, believed by the museum to be the first preserved SD50.^[2]

References

^ "Coming to Terms With EMD's SD50". Trains Magazine. May 2005. pp. 24–25.
^ ^a ^b ^c Smedley, Steve (2 November 2022). "Illinois Railway Museum acquires SD50". Trains Magazine. Retrieved 3 November 2022.
^ Super Series Locomotives for Hamersley Iron Network February 1981 page 27
^ Hammersley Loco Update Railway Digest November 1998 pages 33, 36
^ Here & There Australian Railway Historical Society Bulletin issue 771 January 2002 page 32
^ Oberg, Leon (2010). Locomotives of Australia 1850s-2010s. Kenthurst: Rosenberg Publishing. pp. 390–391. ISBN 9781921719011.
^ Motive Power Roundup Motive Power issue 119 September 2018 page 104

External links

Media related to EMD SD50 locomotives at Wikimedia Commons

Lytle, Stan. EMD SD50 list. Retrieved 16 February 2005.
TrainWeb.com. The Unofficial EMD homepage. Retrieved 7 January 2005. Contains fairly complete builders' records for EMD production.
Union Pacific Railroad Locomotive Department (1994). Locomotive Diagram Book. Union Pacific.
Electo-Motive Division of General Motors (1980). SD50 Operator's Manual 1st Edition November 1980. Electro-Motive Diesel.